This disclosure relates to a method of monitoring for combustion misfire events in engines or other systems with continual periodic combustion events, and related devices.
In periodic combustion processes, such as those in internal combustion engines, combustion may not take place properly under certain conditions. For example, combustion misfire events occur when the air and fuel mixture is off ratio or improperly mixed and does not combust properly during a given cycle. These misfires may also be due to various electro-mechanical failures such as inadequate firing of the spark plug, malfunctioning fuel injectors, or valve operation anomalies, etc.
Combustion misfires may result in damage to the exhaust management components. Often such phenomena take place intermittently, yet may over time degrade catalyst functionality and/or have a significant impact on the engine and/or emission system performance. Accordingly, it is desirable to detect when combustion misfire events occur in order for corrective measures to be implemented. Currently, pressure sensors located in the compression chamber are used to detect misfire events. However, such pressure sensors are expensive due to the need to design them for the harsh environment of the combustion chambers, and are therefore primarily used for research and high-end vehicles. Combustion misfire events may also be detected by monitoring the angular velocity of the engine's crankshaft for minor variations in the expected rotation of the crankshaft as the result of misfiring; however, this approach requires complex algorithms to deal with the high signal to noise ratio inherent in this approach, and for some applications (e.g., motorcycles) road conditions my create high signal to noise ratio errors, making this approach impractical. Combustion misfire events may also be detected by monitoring analysis of the ionization current in the sparkplug circuit and/or optical measurement of the combustion process, both of which are better suited to basic research than commercial products.
As such, there remains a need for alternative combustion misfire sensors for combustion engines, advantageously one that can be placed outside of the combustion chamber, such as in the exhaust plenum.